JPH05105989A - High strength stainless cold rolled steel strip excellent in formability and fatigue property and giving high strength by aging treatment and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a high strength stainless steel strip simultaneously excellent in formability and fatigue properties. CONSTITUTION:This cover is a stainless cold rolled steel strip contg., by weight, <=0.20% C, >1.0 to 5.0% Si, <=4.0% Mn, 4.0 to 10.0% Ni, 12.0 to 20.0% Cr and <=0.03% N, furthermore, as occasion requires, contg. one or two kinds of <=3.0% Mo or 0.5 to 3.0% Cu and in which each content is regulated so that the value of M conforming to the formula of M=330-(480XC%)-(2XSi%)-(10XMn%)-(14XNi%)--(5.7XCr%)-(5XMo%)-(14XCu%)-( 320XN%) will be regulated to >=35 and the balance Fe with inevitable impurities and having <=0.5mum surface roughness. This cold rolled steel strip is manufactured by annealing a hot rolled sheet having the above chemical component value, thereafter regulating its surface roughness to <=8mum in 10 point average roughness Rz, subjecting it to rolling and bright annealing for required times so that the total draft from the hot rolled sheet to a steel strip as a final product will be regulated to >=80% and executing temper rolling of >=30%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold-rolled stainless steel strip having high strength and excellent formability and fatigue properties. The stainless steel strip obtained by the present invention is a material suitable for leaf springs and coil springs that are required to have corrosion resistance as well as fatigue properties, and also to be formed spring parts that are required to have moldability in addition to high strength and fatigue properties. is there.
For example, it exhibits excellent properties for ID saw blades, retractor springs, auto fasteners, metal gasket members for engines of automobiles and motorcycles.

[0002]

2. Description of the Related Art Conventionally, as a material for spring parts made of stainless steel, work-hardening type metastable austenitic stainless steel which can easily obtain high strength by cold working, for example,
SUS301 and SUS304 have been widely used. These steels show two phases of austenite phase and martensite phase by cold working, show appropriate strength and ductility, and have excellent corrosion resistance. Since its strength largely depends on the cold working amount, it is necessary to carry out high temper rolling in order to obtain high strength.

[0003] The temper rolling of these steels is usually carried out in the atmosphere while being annealed and pickled. Even after the hot rolling annealing and the polishing treatment, the annealing pickling was usually performed in either the intermediate annealing or the temper rolling annealing.

[0004]

For spring applications requiring high strength, those which do not require much processing such as ID saw blades, leaf springs, coil springs, etc., and auto fasteners, engines for automobiles and motorcycles, etc. Some metal gasket members for use are used after being molded. All of these require high strength and excellent fatigue and spring properties, but the latter requires more formability.

However, in typical stainless steels for springs SUS301 and SUS304 which have been conventionally used for these applications, it is necessary to carry out high temper rolling in order to obtain high strength. There was a problem that the moldability deteriorated and the moldability was poor. For this reason, when importance is attached to moldability, it was unavoidable to lower the strength level to ensure moldability. As a result, the fatigue life is shortened in applications where repeated stress is applied.

Further, in the conventional material, the annealing pickling before temper rolling is performed as described above, but the pickling causes selective corrosion of grain boundaries, resulting in a decrease in fatigue strength.
There is also a method of polishing and then temper rolling in order to remove this grain boundary selective corrosion, but also in this case, there was a problem that the fatigue strength decreased due to the presence of polishing grains.

In a coil spring such as a retractor, the bending radius tends to become smaller with the miniaturization of parts and the like, and as a result, the surface stress becomes higher. If there are surface defects due to the residual, there is a problem that the useful life is shortened remarkably, and there are some that cannot be used depending on the application.

As described above, the conventional material manufactured by the conventional manufacturing method cannot obtain sufficient fatigue properties and is not sufficient in terms of moldability.

Therefore, the object of the present invention is to
The purpose is to obtain a stainless steel material with excellent fatigue properties while maintaining the formability. In the field of spring parts that require high fatigue strength, which conventional materials cannot withstand, and also after forming is used. To provide new materials in the field of spring components.

[0010]

According to the present invention, the weight percent is
C: 0.20% or less, Si: more than 1.0% and 5.0% or less, Mn: 4.0% or less, Ni: 4.0 to 10.0%, Cr: 12.0 to 20.0
%, N: 0.30% or less, depending on the case,
Mo less than 3.0% or 0.5 to 3.0% Cu, 1 or 2
Including seeds, and M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14
XNi%)-(5.7xCr%)-(5xMo%)-(14xCu%)-
C, Si, Mn, Ni, C so that M according to the formula of (320 × N%) becomes 35 or more
The amount of r, Mo, Cu, N is adjusted, the balance is Fe and unavoidable impurities, and the surface roughness is 0.5 μm or less. Excellent in formability and fatigue properties, and high strength that exhibits high strength by aging treatment. Provide stainless cold rolled steel strip. This steel exhibits an austenite structure in the solution heat treated state during manufacturing.

The high-strength stainless cold-rolled steel strip according to the present invention is obtained by annealing a hot-rolled steel sheet having the above-mentioned chemical composition value and polishing it to a surface roughness of 10 μm average roughness R _Z of 8 μm or less. It can be advantageously manufactured by performing necessary number of rollings and bright annealing so that the total rolling rate from the hot rolled sheet to the final product steel strip is 80% or more, and then performing temper rolling of 30% or more. In the cold rolling before temper rolling, the 10-point average roughness R _Z is 2 μm or less and the center line peak height P _P is at least 2 passes before the final pass including the final pass (1).
The work is performed by using a work roll having a surface roughness satisfying the relation of the formula, and in temper rolling, R _Z is 1.0 μm or less and the center line peak height P in all passes from the initial pass to the final pass.
_It is preferable to use a work roll whose surface roughness _P satisfies the following relationship (1). P _P ≤ (R _Z / 2) x 1.25 (1)

[Detailed Description of the Invention] The steel of the present invention has a suitable C, N content.
The alloy composition has the amount and γ stability, and high strength can be obtained even at a low temper rolling rate, and the surface roughness of temper rolling can be minimized to improve the formability and fatigue characteristics. Is. Furthermore, high strength and high spring limit values are obtained after aging treatment. It should be noted that during the aging treatment, the increase in age hardening degree due to the addition of N can be effectively utilized, and higher strength can be expressed by the addition of Si. If higher strength is required after aging treatment, Mo and Cu are added as age hardening elements.

According to the present invention, after the hot rolled sheet is annealed, it is polished, and the rolling method and the annealing method are defined as described above, so that an excellent surface state can be manufactured and the fatigue characteristics are excellent. Not only does it provide high strength stainless steel strips, but it also prevents the occurrence of micro cracks in the processed parts of parts requiring higher strength and moldability, such as auto fasteners and metal gaskets. Then
The fatigue life after that can also be improved. Especially Si
Of added fine and dense even at low temper rolling rate alpha ^- (strain-induced martensite) phase that may be distributed and then found that can increase the strength increase due to aging by adding N and Si, moderate temper One of the features of the present invention is that the formability and high fatigue properties are imparted by the rolling ratio. The outline of the reason for limiting the composition range of the steel according to the present invention is as follows.

C is an austenite forming element and is extremely effective in suppressing δ-ferrite formed at high temperature and strengthening the martensite phase induced by cold working, but as in the steel of the present invention, it is better formed after temper rolling. If the strengthening by cold working is too significant to obtain workability, the formability becomes poor. Therefore, C is set to 0.20% or less.

Although Si is effective as a deoxidizing agent, it is an important element for inducing and strengthening the martensite phase by cold working, and is also an important element for strengthening by aging treatment. Therefore, addition of more than 1.0% is required. However, if it is made too high, the formation of δ-ferrite is promoted, and the effect is small for the added amount, so the upper limit was made 5.0%. More preferably 1.0%
Exceeds 3.0% or less.

Mn works effectively also as a deoxidizing agent, but it is an element that controls the stability of the austenite phase, and its utilization is considered in balance with other elements. In the present invention steel
Utilization with Mn amount can be achieved up to 4.0%. However, since high strength and moldability are important, it is preferable that the amount of Mn is less than 0.5% and the formation of inclusions such as MnS is avoided as much as possible, especially for those with severe moldability.

Cr is an essential component for corrosion resistance. At least 12% or more is required to impart the intended corrosion resistance and heat resistance. However, since Cr is a ferrite-producing element, if it is made too high, a large amount of δ-ferrite will be produced at high temperatures. Therefore, in order to suppress the δ-ferrite phase, it is necessary to add austenite forming elements (C, N, Ni, Mn, etc.) in an amount commensurate with that, but if a large amount of austenite forming element is added, the austenite phase at room temperature will be It is stable and high strength cannot be obtained after cold working or aging treatment. Because of this, Cr
Was set to 20%.

Ni is an essential component for obtaining an austenite phase at high temperature and room temperature, but in the present invention, even in a low cold work in order to obtain a better formability by forming a metastable austenite phase at room temperature. It should be possible to induce a proper martensite phase, which enables to obtain high strength. In the present invention, when Ni is lower than 4%, a large amount of δ-ferrite phase is generated at high temperature, and a martensite phase other than the austenite phase is easily generated at room temperature. If it exceeds 10%, the martensite phase is less likely to be induced by cold working. Therefore, the Ni content is set to 4.0 to 10.0%. It is more preferably 5.0 to 8.0%.

Mo increases the base hardness of the steel and also increases the hardness after aging treatment, and therefore works effectively in obtaining high strength. However, since it is a ferrite former, if it is added in a large amount, the δ-ferrite phase will crystallize, which will rather cause a decrease in strength, so the upper limit was made 3.0%.

Cu hardens the steel by interacting with Si during the aging treatment. If the amount is too small, the effect is small. If the amount is too large, the hot workability is impaired and cracking occurs.
It was set to 5 to 3.0%.

Regarding S, since MnS is produced in the presence of Mn and causes deterioration of workability such as ductility and bending, it is preferable that Mn and S are lower in a region where the thin plate is difficult to form. ..

M value: 35 or more C, Si, Mn, Ni, Cr, Mo, Cu and N are contained in the above range, but each component is adjusted so that the M value according to the following formula (1) becomes 35 or more. Adjust. M = 330- (480xC%)-(2xSi%)-(10xMn%)-(14xNi%)-(5.7xCr%)-(5xMo%)-(14xCu %) − (320 × N%) ··· (1) The constant of this component value was confirmed in the laboratory during the development of the present invention. This M value serves as an index of austenite stability. At a value of 35 or less, it is necessary to perform strong cold working at room temperature in order to obtain high strength after cold rolling or aging treatment, and ductility decreases. However, the desired moldability cannot be obtained. Therefore, the M value needs to be 35 or more.

The chemical components are adjusted within the above ranges. In addition to the above components, Ca and RE added as deoxidizing agents are also included.
M, B (0.01% or less) effective in improving hot workability,
Impurities that are inevitably mixed can be contained.
If high strength is to be obtained after aging treatment, Ti, Nb,
V can be added singly or in combination with the upper limit of 1.0%.

The steel according to the present invention adjusted to the above range has substantially the austenite structure in its liquefied state. The steel strip according to the present invention is manufactured by the following manufacturing method.

First, a hot-rolled sheet (hot-rolled steel strip) of this steel is manufactured. Using this hot-rolled sheet as a starting material, it is manufactured by the steps of annealing the hot-rolled sheet, polishing, cold rolling and bright annealing the required number of times, and temper rolling. At that time, the surface roughness after temper rolling is preferably 0.5 μm or less by optimizing the surface roughness of the steel after the polishing treatment and the surface roughness of the work roll during rolling. Therefore, the following method is adopted.

After the hot rolled sheet is annealed, it is polished to a surface roughness of 10 μm average roughness R _Z of 8 μm or less. Then, in the subsequent cold rolling, the 10-point average roughness R _Z is 2 μm or less and P _P (= center line peak height) ≦ (R _{Z / 2)} x 1.2
Roll using a work roll having a surface roughness that satisfies the relational expression (5). In addition, the work rolls used in temper rolling have R _{Z in} all passes from the initial pass to the final pass.
1.0 μm or less and P _P (= height of peak of center line) ≦ (R _Z / 2) × 1.
Use a work roll with a surface roughness that satisfies the relationship of 25. And the total rolling rate from hot rolled sheet to final product is 80%
Above, and temper rolling of 30% or more. As a result, it is possible to obtain stainless steel suitable for a spring material that has excellent formability and fatigue characteristics while obtaining strength equal to or higher than that of conventional steel.

Here, in the cold rolling process before temper rolling,
Rolling using a work roll having a 10-point average roughness R _Z of 2 μm or less and a surface roughness satisfying the relational expression P _P ≦ (R _Z /2)×1.25 from at least 2 passes before including the final pass. The reason is that when the temper rolling rate is kept low to obtain high formability, if the surface roughness of the rolling roll is rough before temper rolling, the unevenness printed at that time is not affected even after temper rolling. This is because it remains, and even if the surface roughness of the rolling roll at the time of temper rolling is reduced, it is not possible to obtain high fatigue properties, which is one of the objects of the present invention. Further, in the temper rolling work roll is set to _P P ≦ (R _Z /2)×1.25 in all paths, which will pitch is narrow polishing marks irregularities sharp accordance R _Z decreases, the P _P This is because if it is not reduced, sufficient strength characteristics cannot be obtained.

The temper rolling ratio varies depending on the strength level after annealing before temper rolling, the stability of the austenite phase, etc., but at a rolling ratio of 30% or less, it is difficult to obtain the target strength and a sufficient surface area is obtained. 30 because the condition and fatigue characteristics cannot be obtained
% Or more. The upper limit is not particularly limited, but is considered to be around 70% in order to achieve the target strength at a lower rolling rate than that of conventional steel and to maintain the formability as much as possible.

The total rolling rate from the hot rolled sheet to the final product is 80
% Or more. This is because the final product is manufactured only by bright annealing, so the initial surface condition affects the final product as well. Therefore, the total rolling rate is set to 80% or more.
When the surface roughness R _max after temper rolling is 0.5 μm or less, the bending workability after temper rolling improves and the fatigue limit of the final product improves, but the surface roughness is achieved through the above manufacturing method. To be done.

As will be shown in Examples described later, according to the manufacturing method of the present invention, a product having a good surface roughness is obtained, the fatigue strength of the smooth portion is further excellent, and the bending forming process after temper rolling is performed. Microcracks do not occur, the fatigue strength of the formed spring parts is high, and the fatigue limit is high. In this respect, the effect is remarkably higher than that of the conventional steel produced by the conventional manufacturing method. In addition, the increase in strength due to aging treatment after temper rolling is larger than that of conventional steel due to the addition of N, Si, Mo, Cu, etc. If the same strength is obtained after aging treatment,
It is possible to reduce the strength level after temper rolling, and it is possible to provide a product with excellent formability.

Further, in order to obtain strength characteristics as a spring component, aging treatment is performed after the forming process, and the condition is 300
The temperature range is ℃ to 600 ℃. At temperatures lower than 300 ° C, it takes a long time to obtain the target strength level, which is not economical. At temperatures above 600 ° C, a large amount of recovery occurs before the strength rises, and the strength required for spring parts cannot be obtained. The aging treatment time is 10 seconds or more. If the time is shorter than this, sufficient strength characteristics cannot be obtained. The upper limit is not particularly limited, but about 1 hour is preferable from the viewpoint of manufacturing cost.

[0032]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples.

Of the steels having the chemical compositions shown in Table 1, the present invention materials Z1 and Z2 and the conventional material A were melted according to a common melting method to manufacture a slab having a thickness of 200 mmt, and 3.5 m by hot rolling.
It was a hot coil of mt thickness. After hot-rolled sheet annealing and polishing, 2
After cold-rolling and annealing twice, temper rolling was performed to obtain a cold-rolled steel sheet of 0.25 mmt.

On the other hand, the invention materials Z3 to Z5 and the comparative materials (a, b) were melted by ordinary atmospheric melting to prepare a 200 kg steel ingot, which was forged and hot rolled into a hot rolled sheet of 3.5 mmt. After the hot-rolled sheet was annealed and polished, it was cold-rolled twice, annealed twice, and temper-rolled to obtain a cold-rolled steel sheet of 0.25 mmt.

In addition, the manufacturing method applied to each test material is summarized below. Bright annealing for the purpose of solution treatment before temper rolling was performed at a temperature of 1070 ° C. As for the rolling rolls, work rolls satisfying the conditions described in the text were used except for Comparative Method 3.

The method of the present invention: hot rolled sheet annealing / polishing → rolling (3.5 /
1.5mmt) → bright annealing → rolling (1.5 / 0.40 to 0.50mmt) → bright annealing → temper rolling (0.40 to 0.50 / 0.25mmt) Conventional method 1: hot rolled sheet annealing / polishing → rolling (3.5 / 1.5mmt) → Atmospheric annealing pickling → rolling (1.5 / 0.315 ~ 0.714mmt) → atmospheric annealing
Pickling → Temper rolling (0.315 to 0.714 / 0.25mmt) Conventional method 2: Hot rolled sheet annealing / Pickling → Rolling (3.5 / 1.5mmt) → Atmospheric annealing / Pickling → Rolling (1.5 / 0.455 to 0.625mmt) → Atmospheric annealing
Polishing → Temper rolling (0.455 ~ 0.625 / 0.25mmt) Comparative method 1: Hot rolled sheet annealing / pickling → Rolling (3.5 / 1.5mmt) → Atmospheric annealing / polishing → Rolling (1.5 / 0.455mmt) → Bright annealing → Tuning Comparative rolling method 2: Hot-rolled sheet annealing / polishing → rolling (3.5 / 1.5mmt) → bright annealing → rolling (1.5 / 0.33mmt) → bright annealing → temper rolling (0.33 /
0.25 mmt) Comparative method 3: P _p ≦ (R _z / 2) × 1.
The method is the same as the method of the present invention except that the one which does not satisfy 25 is used. Table 2 shows the relationship between each test material, each manufacturing method, and the total rolling rate and temper rolling rate.

The temper-rolled material thus obtained was subjected to the following test by collecting samples from the temper-rolled material as it was and from the steel sheet which had been subjected to an aging treatment at 400 ° C. for 30 minutes. did.

A tensile test was performed using each of the collected samples, a forming workability test was performed on the as-tempered sample before aging treatment, and a fatigue test was performed on the sample after aging treatment. These results are also shown in Table 2. In addition, Table 2 also shows the surface roughness after temper rolling.

As shown in FIG. 5, the evaluation of the moldability was carried out by using the die 1 and the punch 2 in a 90-degree bending test to test the test piece 3 at 90 degrees, and the outside R portion (R = 0.2 mm) was observed, and evaluation was made with no microcracks (○ mark), with fine microcracks (△ mark), and with cracks (× mark).

Regarding the fatigue characteristics, in the thin plate bending fatigue test shown in FIG. 6, a test pulley 5 and a drive pulley 6 were used.
Set the test piece 3 via the dummy band 4 between the two, adjust the stress by changing the diameter of the test pulley 5, and repeat the repeated motion to give the test piece a variable stress until the fracture. The number of repetitions was evaluated. Table 2 shows the number of repetitions until fracture at a repeated bending stress of 100 kg / mm ² .

[0041]

[Table 1]

[0042]

[Table 2]

From the results shown in Table 2, it is clear that:
First of all, among the steels used for the verification, those produced by the method of the present invention with the material of the present invention do not cause any micro-cracks or cracks during forming, and have sufficient tensile strength and fatigue strength after aging treatment. have.

In order to obtain the same tensile properties as the material of the present invention after aging treatment in the conventional material, it is necessary to carry out high temper rolling as in Nos. 11 and 13, and cracks occur during the forming process. In order to improve the formability, it is necessary to lower the temper rolling rate, but in this case, as in No. 12, the tensile strength after aging treatment is low and the fatigue strength is also low.

No. 14 of the comparative material has a low M value and is out of Table 1.
No. a steel manufactured by the conventional method 1 requires high temper rolling to obtain tensile properties equivalent to those of the material of the present invention after aging treatment. become. Nos. 15 and 16 are steel b of Table 1 that exhibits a martensitic structure after solution treatment. In this case, even if the temper rolling ratio is low, after aging treatment, almost the same tensile properties as the material of the present invention are obtained. However, due to the matrix martensitic structure, ductility is poor and cracking occurs during forming.

FIG. 1 is a photograph showing the surface condition of the steel No. 6 of the invention steel Z1 manufactured by the conventional method 1. The selective corrosion of grain boundaries due to pickling after annealing is recognized. In particular, in the present invention, the composition is designed so that the temper rolling rate can be suppressed to be low in order to enhance the molding workability, so this tendency can be clearly seen.

FIG. 2 shows the result of No. 2 which was subjected to temper rolling after removing the selective corrosion of grain boundaries observed in Conventional Method 1 by polishing.
This is a photograph showing the surface condition of No. 7, in which the selective corrosion of grain boundaries is removed, but after the temper rolling, polishing marks remain and the surface condition is poor, and the surface roughness is also bad with R _max of 1.31 μm.

FIG. 3 shows No. 2 manufactured by the method of the present invention.
Fig. 4 is a photograph showing the surface condition of the hot-rolled sheet. In this case, the hot-rolled sheet was manufactured without annealing after polishing, and was rolled using a roll with a small surface roughness. Since the rolling rate is high and 30% or more of temper rolling is applied, the surface condition is good and the surface roughness is small.

In order to investigate the influence of these surface conditions on the fatigue characteristics, a strip-shaped test piece having a length of 150 mm and a width of 10 mm was sampled at right angles to the rolling direction, and the end face was polished with No. 600 emery paper, A repeated thin plate bending fatigue test was conducted in the same manner as above, and the effect of the surface condition on the fatigue properties was investigated. The results are shown in Fig. 4.

FIG. 4 shows the products manufactured by the method of the present invention (Example 1 of the present invention in Table 2) and those manufactured by the conventional methods 1 and 2 (Comparative Examples No. 6 and 7 of Table 2). The magnitude of the bending stress applied on the vertical axis and the number of repetitions until fracture are plotted on the horizontal axis for comparison. As seen in FIG. 4, the method according to the present invention has high fatigue strength and fatigue limit, and the influence of the surface condition is clear.

Table 2 shows the results of each fatigue test. In each of the products manufactured by the method of the present invention using the material of the present invention, the surface roughness is 0.5 μm or less at R _max and the surface condition is good. , and the exhibit high fatigue properties without breaking any in tests under stress of 100 kg / mm ^2, is excellent in terms of moldability.

However, even if the material of the present invention is used, as shown in the comparative example, the products manufactured by the conventional methods 1 and 2 and the comparative methods 1, 2 and 3 have good moldability, but have fatigue characteristics. Both were inferior and fractured within the range of 50 to 230 × 10 ⁴ times.

In Comparative Example No. 6, although the surface roughness is fairly good, the grain boundary selective corrosion type surface state is shown, and therefore the fatigue strength is low.

In Comparative Example No. 7, the selective corrosion of the grain boundaries was removed by polishing and then temper rolling was carried out. However, after the temper rolling, polishing marks remained and the surface condition was bad and the fatigue strength was extremely poor. There is.

Comparative Example No. 8 was polished at 1.5 mmt after the first annealing, but a sufficient surface condition was obtained because the total rolling ratio from polishing to the product sheet thickness was low. No, it is inferior in fatigue characteristics.

Comparative Example No. 9 had a temper rolling ratio outside the range of the present invention, but the original fatigue characteristics were obtained because the strength level was low and sufficient surface roughness could not be obtained. Not not.

No. 10 has a rolling roll _Rz = 2 before temper rolling.
μm, P _p = (R _z /2)×1.5, which does not satisfy the expression (1) (Comparative method 3), but a sufficient surface condition cannot be obtained and the fatigue property is poor.

No. 12 manufactured by reducing the temper rolling rate in order to obtain good forming workability with the conventional material cannot obtain sufficient fatigue properties because the tensile strength after aging treatment is low. ..

No. 16 using the comparative material (b) has sufficient properties in terms of strength, but the final temper rolling rate is as low as 25%, so the surface condition is a little poor and sufficient. Fatigue properties are not obtained.

From the above, it is necessary for the manufacturing method according to the present invention to satisfy the characteristics of both the formability and the fatigue characteristics, and the composition should be within the component range limited by the present invention. Is recognized.

[0061]

As described in detail above, the steel of the present invention has a greater strength increase due to aging treatment than the conventional stainless steel for springs, SUS301 series steel, so the strength before aging treatment can be reduced. Therefore, it has more excellent moldability.
Moreover, after the aging treatment, high strength can be exhibited and a high strength spring material can be obtained. Further, it is possible to provide a spring component having a good surface condition, and it is possible to provide a more stable spring component as compared with the conventional one due to the improvement in fatigue strength accompanying this. For example, it is clear that even in applications where molding is applied such as auto fasteners and metal gaskets, a product with a significantly long life can be obtained due to its excellent moldability and fatigue properties. In addition, it is possible to manufacture a formed spring component that could not be manufactured with conventional steel. Furthermore, the manufacturing method is not so different from the conventional one, and there is no difference in cost from the conventional steel, and the industrial benefit is large.

[Brief description of drawings]

FIG. 1 is a photograph of the metal surface of Comparative Example No. 6.

FIG. 2 is a photograph of the metal surface of Comparative Example No. 7.

FIG. 3 is a photograph of the metal surface of Inventive Example No. 2.

FIG. 4 is a diagram showing the results of repeated thin plate bending fatigue tests of the invention material Z1 manufactured by the conventional method 1 and the invention method, and the invention material Z4 manufactured by the conventional method 2.

FIG. 5 is a schematic cross-sectional view showing a 90-degree butt bending test method for evaluating moldability.

FIG. 6 is a diagram for explaining the outline of a thin plate bending fatigue test.

[Explanation of symbols]

 1 Die 2 Punch 3 Test piece 4 Dummy band 5 Test pulley 6 Drive pulley

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 14, 1992

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a photograph showing the metal structure of Comparative Example No. 6.

FIG. 2 is a photograph showing the metal structure of Comparative Example No. 7.

FIG. 3 is a photograph showing the metallographic structure of Inventive Example No. 2.

FIG. 4 is a diagram showing the results of repeated thin plate bending fatigue tests of the invention material Z1 manufactured by the conventional method 1 and the invention method, and the invention material Z4 manufactured by the conventional method 2.

FIG. 5 is a schematic cross-sectional view showing a 90-degree butt bending test method for evaluating moldability.

FIG. 6 is a diagram for explaining the outline of a thin plate bending fatigue test.

[Explanation of symbols] 1 die 2 punch 3 test piece 4 dummy band 5 test pulley 6 drive pulley

Claims (6)

[Claims] 1. In weight%, C: 0.20% or less, Si:
Over 1.0% to 5.0% or less, Mn: 4.0% or less, Ni: 4.0 to 10.0
%, Cr: 12.0 to 20.0%, N: 0.30% or less, and M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14
XNi%)-(5.7xCr%)-(320xN%) so that the M value is 35 or more, C, Si, Mn, Ni,
High strength stainless cold rolled steel with controlled Cr and N contents, balance of Fe and inevitable impurities, surface roughness of 0.5 μm or less, excellent formability and fatigue properties, and high strength by aging treatment. band. 2. In weight%, C: 0.20% or less, Si:
Over 1.0% to 5.0% or less, Mn: 4.0% or less, Ni: 4.0 to 10.0
%, Cr: 12.0 to 20.0%, N: 0.30% or less, further 3.0%
The following Mo or 0.5 to 3.0% Cu of 1 or 2 is included, and M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14
XNi%)-(5.7xCr%)-(5xMo%)-(14xCu%)-
C, Si, Mn, Ni, C so that M according to the formula of (320 × N%) becomes 35 or more
The amount of r, Mo, Cu, N is adjusted, the balance is Fe and unavoidable impurities, and the surface roughness is 0.5 μm or less. Excellent in formability and fatigue properties, and high strength that exhibits high strength by aging treatment. Stainless cold rolled steel strip. 3. In weight%, C: 0.20% or less, Si:
Over 1.0% to 5.0% or less, Mn: 4.0% or less, Ni: 4.0 to 10.0
%, Cr: 12.0 to 20.0%, N: 0.30% or less, and M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14
XNi%)-(5.7xCr%)-(320xN%) so that the M value is 35 or more, C, Si, Mn, Ni,
After the amount of Cr and N was adjusted, and the balance was Fe and the inevitable impurities, the hot rolled sheet of stainless steel was annealed and then polished to a surface roughness of 10 points average roughness R _Z of 8 μm or less,
After performing the necessary number of rollings and bright annealings so that the total rolling rate from the hot rolled sheet to the final product steel strip is 80% or more,
A method for producing a high-strength stainless steel strip, which is subjected to temper rolling of 30% or more, is excellent in formability and fatigue properties, and exhibits high strength by aging treatment. 4. In weight%, C: 0.20% or less, Si:
Over 1.0% to 5.0% or less, Mn: 4.0% or less, Ni: 4.0 to 10.0
%, Cr: 12.0 to 20.0%, N: 0.30% or less, further 3.0% or less of Mo or 0.5 to 3.0% Cu of one or two kinds, and M = 330− (480 × C%) − ( 2 x Si%)-(10 x Mn%)-(14
XNi%)-(5.7xCr%)-(5xMo%)-(14xCu%)-
C, Si, Mn, Ni, C so that M according to the formula of (320 × N%) becomes 35 or more
After the amount of r, Mo, Cu, N was adjusted, and the balance was made of Fe and inevitable impurities, the hot-rolled sheet of stainless steel was annealed and then polished to obtain a surface roughness of 10 μm average roughness R _Z of 8 μm or less. Total rolling ratio from hot rolled sheet to final product steel strip is 80%
After performing the necessary number of rollings and bright annealing as described above, and temper-rolling at 30% or more, it has excellent formability and fatigue characteristics, and high strength that develops high strength by aging treatment. Manufacturing method of stainless steel strip. 5. The cold rolling before temper rolling has a 10-point average roughness R _Z of 2 μm before at least two passes including the final pass.
Below, and the center line peak height P _P is performed using a work roll having a surface roughness satisfying the relationship of the following formula (1), and temper rolling is performed in all passes from the initial pass to the final pass.
The method for producing a high-strength stainless steel strip according to claim 3 or 4, wherein R _Z is 1.0 µm or less and the height of center line P _P is a work roll having a surface roughness satisfying the following relationship (1). .. P _P ≤ (R _Z / 2) x 1.25 (1) 6. The aging treatment is performed after forming into a desired shape 30
The manufacturing method according to claim 3, 4 or 5, which is applied in a temperature range of 0 ° C to 600 ° C for 10 seconds or more.